The present invention concerns transponders associated with identification systems or transactions of various natures. More particularly, the present invention concerns a transponder intended for several different applications.
Currently, a transponder is generally intended for a single specific application, in particular for bank transactions, for the payment of certain services or goods, or for recognizing or identifying objects or individuals. The transponder may take different forms, in particular the form of a card. Thus, there are bank cards, telephone cards and access cards for certain buildings or means of transport.
The multiplication of different applications generates a multiplication of the cards or transponders with which the user is burdened. Indeed, these cards or transponders generally have to be carried by the user as he moves around. This is the reason why, within the scope of the present invention, a transponder or card intended for several different applications is proposed. Hereinafter, only the term transponder will be used, defined as a contactless communication device with a reader or transmitter, in particular a card.
However, a multi-application transponder is confronted with a problem of different security levels for the different applications. Indeed, certain applications, in particular those linked to monetary transactions, require a high level of security.
Conversely other applications do not require such a security level. An important parameter involved in the notion of security for a transponder system is the maximum communication distance between a transponder and a reader of the system. Thus, certain applications are implanted in systems allowing only short, or very short distance communication, so as to prevent, in particular, a receiver outside the system being able to receive the electromagnetic signals exchanged between the reader and the transponder. Conversely, other applications, in particular in the field of identifying people or objects, are implanted in systems allowing at least medium distance communication, i.e. greater then ten or so centimeters.
Given that the transponders known to those skilled in the art, in particular passive type transponders, are arranged with an antenna associated with an electronic unit allowing communication at a pre-defined maximum distance for a determined power of the activation signal transmitted by the reader, those skilled in the art cannot easily provide a passive transponder for various applications requiring different maximum communication distances.
The object of the present invention is to overcome this major drawback.
The present invention therefore concerns a transponder including a communication antenna and an electronic unit arranged so as to control several different applications, characterized in that it includes means for varying the maximum communication distance with a reader as a function of the application selected or activated among said different applications.
In a preferred embodiment, the means for varying the maximum communication distance include means for varying the equivalent impedance of the transponder""s electronic unit.
In a variant of this embodiment, the means for varying this equivalent impedance include means for varying the equivalent resistance of the electronic unit so as to vary the current consumed by the latter and thus the load.